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Author Topic:   Human Brain Evolution Was a 'Special Event'
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 8 of 65 (352707)
09-27-2006 8:45 PM
Reply to: Message 1 by skepticfaith
09-27-2006 4:39 PM


A couple of points ...
(1) The 20 to 25 million years is based on the divergence of the human lineage from that of the macaque, and does not say when in that period the mutations occurred. Similar studies show much more brain mutation\selection in the human lineage than in the chimp lineage, cutting the time period down to 6 to 7 million years, except that we don't know the base values for macaque to chimp and how much more mutation\selection is evident in chimps vs macaques.
My feeling is that including chimps would show a higher rate and (but not all) of the mutations\selection occurred since {chimp\human} split. My reason for this feeling is both the major change in brain size in Homo sapiens (as noted in the article) and because:
(2) Sexual selection operates on every mating\generation. This means that any mechanism that employs sexual selection will consistently show a higher rate of selection than one that only employs survival. Survival is only tested in bad times, so it does not provide and selection pressure in good times (beyond basic viability).
The human brain shows signs of classical Fisherian run-away sexual selection (from the article linked in OP):
quote:
Humans have extraordinarily large and complex brains, even when compared with macaques and other non-human primates. The human brain is several times larger than that of the macaque”even after correcting for body size”and “it is far more complicated in terms of structure,” said Lahn.
So large it endangers the life of the mother at birth. So large it can't get larger (unless all births are by C-section and we 'evolve' a new technique for birth to avoid this problem).
(3) rates of mutation and "genetic clocks" are basically post hoc ergo propter hoc calculations rather than predictive in values.
I have trouble with "genetic clock" type inferences that seem to fall back into old stereotypical gradualism models of evolution that ignore (a) differential rates of selection beteen sexual and survival and (b) ignore periods of intense survival selection that can cause punk-eek type evolution rate changes.
Example again from the article:
quote:
They then obtained the rate of evolution for that gene by scaling the number of DNA changes to the amount of evolutionary time taken to make those changes.
They only consider the average rates within each period. There could easily be a range of rates that depend more on selection pressure acting on the populations than on the rates of mutation, so what you are seeing is not a change in rates of mutation, but an increased selection for change instead of for stasis.
Until some studies are done to delineate the actual maximum (minimum = 0) rates of changes possible and compare those to actual selection mechanisms and mutation rates, the whole concept of {faster\slower} is ill-defined and sloppy thinking.
In my, of course, humble (but sometimes arrogant) opinion ... (imochbsao?)
(4) the selection is for is not necessarily 'intelligence' in spite of what the article says:
quote:
“The human lineage appears to have been subjected to very different selective regimes compared to most other lineages,” said Lahn. “Selection for greater intelligence and hence larger and more complex brains is far more intense during human evolution than during the evolution of other mammals.”
I think this is more human hubris than fact. We like to think we are so much smarter than any other animal eh? Yet the range of human intelligence still overlaps the ranges in other animals.
If the selection is sexual, driven by mating preferences rather than survival, then the critical elements are the ones that benefit mating: creativity, dance, song, etc -- and brain capacity for 'intelligence' is a by-product. For anecdotal evidence that this is so, just look at who is usually listed as the 'sexiest' (= most matable) people: actors, artists, dancers, rock stars, and NOT nobel prize winners.
Enjoy.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
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Message 11 of 65 (352731)
09-27-2006 11:12 PM
Reply to: Message 10 by skepticfaith
09-27-2006 10:57 PM


Re: The Gap
... we know that the Australopithecus had about the brain size of a chimpanzee.
But we don't know how much brain development separates Chimps and Macaques, so we can't claim it is all since we diverged from Chimps.
And why was suddenly brain size so important, ...
Is it? The real question is "what is important that results in a large brain" eh?

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 35 of 65 (353225)
09-29-2006 6:18 PM
Reply to: Message 21 by skepticfaith
09-28-2006 7:37 PM


brain size evolution ... again ...
It still is remarkable since the history of civilization is over a few thousand years or so, then have any mutations occurred throughout history that we have discovered? Have our brains grown bigger - are we still evolving?
You are talking about the last 4-5k years when homo sapiens has been a species for ~160,000 years and has shown little development in brain size in that period (~3% of our species existence). The time since the start of brain development circa Australopithicus afarensis is ~3 million years. What you would notice in such a brief time is very very small incremental change if any.
The other thing to consider is that the brain size may well be maxed out -- any larger and viable babies cannot be born from living mothers by natural means -- and it is only very very recently that C-sections have become an alternative to natural birth, so further increases lead to deaths of baby or mother.
This forces further brain development to work inside the existing size limits by increasing the ability of the brain to process information.
There is evidence that this too has been occurring, and could well STILL be occurring, as this gets around the size limitations, but you won't see it as readily as growth in brain size.
There was another thread that discussed this in more detail ... Bones of Contentions. ... although it starts out a little differently (on racism).

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 46 of 65 (353508)
10-01-2006 5:59 PM
Reply to: Message 45 by melatonin
09-30-2006 9:03 PM


note ...
If you look at the post with the {Peek} button (it will open another window) you can see how the coding was done.
Note -- it is usually considered bad form to link directly to images on other sites ("deep links") as it can cause high bandwidth use on those sites. There are some options for uploading images (mirroring them), but reference to the original site should also be provided. Admin can help with image hosting.
(another wish-list item -- automatic conversion of all image links to be uploaded - like avatars - and linked to the original site)
Enjoy.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 50 of 65 (362519)
11-07-2006 10:20 PM
Reply to: Message 47 by Hawks
10-01-2006 8:55 PM


Re: Mutations.
There is no must for beneficial mutations to have occured during the time of civilization. And if there were any, they would not have to be increases in brain size.
Also size is not necessarily 'beneficial':
  • a brain can be bigger and still not as well connected
  • a larger human brain can be detrimental when the mother and fetus die in childbirth
  • there are a lot of animals with larger brains than humans
  • size is NOT what is being selected
  • active mutations in connectivity are still occurring
  • the major difference between homo sap brains and the brains of other animals is in the degree of connectedness
The question on brain development in humans is WHAT is being selected.
Enjoy.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 52 of 65 (362589)
11-08-2006 7:47 AM
Reply to: Message 51 by 42
11-08-2006 2:29 AM


So, a concentration of mutations in a few generations is not astounding, and may be seen as special if one chooses to see it that way.
If mutations are random then the distribution of beneficial ones within the full spectrum will also be random.
chaos theory probably explains it
It would be a good start.
If selection operates on mutations beneficial to a certain direction then any random mutations in that direction will be selected when they occur - and will also be randomly distributed over time.
The appearance of clumping is predicted by this mechanism.
Even without discussing whether or not mutations happen at a steady rate, or the rate oscillates around a medium that reacts to change in the environment.
Even without discussing WHAT the selection is for in human brain development.
Enjoy.
Edited by RAZD, : added second quote - hopefully got it right. when you edit you don't get the "message you are replying to" for reference anymore.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
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Message 54 of 65 (362748)
11-08-2006 9:46 PM
Reply to: Message 53 by melatonin
11-08-2006 8:25 PM


... from neanderthals or another archaic homo group.
Perhaps Homo erectus or Homo ergaster?
http://www.dmanisi.org.ge/index.html
quote:
To day we have recovered more than twenty hominid remains in Dmanisi. This includes three mandibles, three hominid skulls and several postcranial parts.
The Dmanisi hominid remains are the first hominids discovered outside of Africa to show clear affinities to African H. ergaster rather than to more typical Asian H. erectus or to any European hominid.
They had basic stone tools, for whatever that is worth.
quote:
No bifaces or developed Oldowan artifacts have been found. Most of the artifacts retain sharp edges suggesting little transport and no refits of flakes or tools were observed. By the basic knapping technique Dmanisi lithic complex clearly belongs to the Oldowan or mode 1 industries. The Dmanisi artifacts are compatible with pre-Acheulean assemblages of East Africa .
Neander is not the only conclusion to reach here. Seems to be a romantic neo-european bias here ...
Enjoy.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 56 of 65 (362856)
11-09-2006 10:28 AM
Reply to: Message 55 by melatonin
11-08-2006 10:14 PM


Re: romantic collective unconscious
Indeed, Pbo says, he will now search for the haplogroup D variant of microcephalin in his own studies of the Neandertal genome.
That would be the test. We had a thread on mtDNA evidence for neander mix, that pretty well showed no mitochondrial mixing, but that did not rule out the possibility of male neander genes.
Mammuthus was involved with the data IIRC.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
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Message 60 of 65 (362971)
11-09-2006 8:42 PM
Reply to: Message 58 by Joman
11-09-2006 3:23 PM


oh. dear.
Welcome to the fray Joman,
I think that what's amazing about the brain isn't it's size but it's cognitive abilities.
Which is only a matter of quantity (not quality) compared to the cognitive ability of other apes or even other animals. A recent article talks about elephant self recognition as one of many examples of cognitive ability in other animals.
Cognitive ability is related to connectedness as well as to size - of the surface area rather than volume (hence the convolutions).
So, when I see a cartoon of a naked man that lived 1oo,ooo years ago looking unsure about, whether or not, the rock in his hand might be a tool, I know that he didn't have the cognitive brain I have.
So you base your understanding of ancient man on cartoons? Interesting.
It seems that brain size is supposed to be the great signature of the evolution of man. I suppose it's because it's the only remnant of the past that can be empirically measured which relates to the brain of man.
Homo neanderthalus had larger brains than Homo sapiens, but were not able to compete with us (even with tools), and there are many other species with larger brains, therefore SIZE is NOT the "signature" you are looking for. A more accurate claim would be cognitive ability, which as you (correctly) note, is not necessarily associated with size.
Even there, we see a gradation between all animals, with several species having individuals with cognitive ability that overlaps those of individual humans at the low end of the human spectrum.
As for what remains as evidence in fossil skulls, it is not just the size of the skull but the size and distribution of different parts of the brain within the skulls as we transitioned from ape ancestor to homo sap, and this can also tell us details about the development of the "special" human brain.
From Message 60:
As far as the genetics of brain size goes, it is not just a matter of size per se, but where that size increases in the intermediate forms.
http://www.massey.ac.nz/~alock/hbook/brain.htm
quote:
With regard to brain reorganization, left-right cerebral hemispheric asymmetries exist in extant pongids and the australopithecines, but neither the pattern nor direction is as strongly developed as in modern or fossil Homo. KNM-ER 1470 shows a strong pattern that may be related to handedness and tool-use/manufacture. The degree of asymmetry appears to increase in later hominids.
The appearance of a more human-like third inferior frontal convolution provides another line of evidence about evolutionary reorganization of the brain.
None of the australopithecine endocasts show this region preserved satisfactorily. There is a consensus among palaeoneurologists that the endocast of the specimen KNM-ER 1470 does show, however, a somewhat more complex and modern-human-like third inferior frontal convolution compared with those of pongids.
Note that specimen KNM-ER 1470 is in the above referenced chart as skull (F).
continuing:
quote:
Unfortunately, later hominid endocasts, including H. habilis and H. erectus through archaic H. sapiens to the present, seldom show the sulcal and gyral patterns faithfully. Thus nothing palaeoneurological can be said with confidence about possible changes with the emergence of anatomically modern H. sapiens. On the other hand, there is nothing striking about Neanderthal brain casts in comparison to more recent H. sapiens, except their slightly larger size, suggesting no significant evolutionary change thereon.
color yellow for empHASis.
So we don't just have brain SIZE for evidence, we also have relative areas and their development and change over time.
KNM-ER 1470 is the "type" fossil for Homo rudolfensis, that lived about 1.8 million years ago and is skull (F) in the picture shown later in this post.
This is a unfortunate state of affairs for the theory of evolution since, the data being discussed (brain size) is so crude that it can't ever rise to the level of scientifically rational extrapolation...er something other than hot air.
I love it when people confuse their misunderstanding of evolution with it being a problem for science.
Evolution is the change in species over time, so when we see evidence for change in species over time, how is that a "problem" for evolution?
And there is plenty of evidence FOR the change in species over time resulting in larger brain capacities in the lineage of human ancestry:

(Source of this picture is 29 Evidences for Macroevolution: Part 1)
The other data (quantity of mutations)only allows analysis of things as they are now.
Except that we can compare the same data for closely related species - chimpanzees, bonobos, gorillas, etcetera, and see what elements were common and what are different.
What convinces me that the theory of evolution is falsified by these circumstances is my belief that man, can't survive, and couldn't have survived without cognitive ability enabling man to use fire, clothing and tools.
So you are convince by your incredulity without any reference to facts or evidence?
In addition to nwr's evidence in Message 59, we also have the record of Darwin in Tierra del Fuego
quote:
Here, two of Captain Cook's men died of the cold. WE went up to the same mountains the same day in the month AS THEY. Here you find the savage in plenty. Picture to yourself a canoe along side of a ship; with two or three men with as many women and a child, perhaps two, all absolutely naked.
And certainly in Africa - where hominids evolved into Homo sap - there is not an issue of needing clothes or fire to keep warm.
Apes also use tools and survive.
Without fire man can't cook, dry out nor keep warm. Man therefore, would've required adequate hair for survival.
Your argument is based on your personal incredulity that this could have occurred. All you prove by this argument is your incredulity and your inability to imagine.
We don't need to imagine clothes in Africa. We don't need to imagine fire to eat food without it, a practice still used in the world today (funny as it may seem).
But, if man once upon a time had adequate hair there wouldn've been any need for clothes and so, any evolution of hair loss would've been immediately selected back out of existence.
When it comes to hair, what you are forgetting (or are ignorant of) is the force of sexual selection, and how it can select for a feature that may have less survival fitness, but gets passed on because it boosts reproductive success.
Selection for a feature that threatens survival in those that best express it while at the same time showing evidence for increased selection in that direction is a signal of (Fisherian) runaway sexual selection. And selection continues to this day for humans to show less hair.
If you are interested in more information on this issue go to Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution, especially Message 44
It is interesting to note that the shame associated with nakedness has no evolutionary rationale.
And it is very interesting to note the total lack of shame in many native people that go naked day after day. All you are doing is projecting your personal (unnatural?) feeling onto others.
The ladies in the (copyright) picture here: "a picture brought back from south africa to australia by my great grandfather in the early 1900s featuring two native girls " are neither shamed nor cold nor huddled around a fire.
I submit that the lack of these three things (fire,clothing,tools) can be proven to be life threatening.
The facts above prove your hypothesis is false, but it is also false on several levels, not least of which is your assumption of all or nothing in these developments, while the evidence shows gradual developments in all those cultural features that benefited the ancestors that used them.
So, how did man survive until he obtained the benefit of cognitive thought?
By ignoring your argument from incredulity and your straw man argument. The way animals in the world today survive in spite of your ignorance of evolution.
BTW...what came first the eye's of man or the holes in his skull in which they fit, and function?
Please take this to a new topic (see Proposed New Topics) so we can discuss how eyes existed before bony skulls, before mammals, before primates, before apes and before humans, without taking this thread off topic and getting a bunch of people suspended for answering such a ... question here.
Enjoy.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
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Message 61 of 65 (366471)
11-28-2006 9:28 AM
Reply to: Message 1 by skepticfaith
09-27-2006 4:39 PM


OOPS -- NOT so "special" after all?
News article from Seattle Times - Nation & WOrld
Tuesday, November 28, 2006 - Page updated at 12:00 AM
Humpbacks have unusual type of brain cells also found in humans
quote:
Humpback whales are unusual among cetaceans for having a type of neural cells in their brains that also are found in humans.
The structure of the neurons, researchers say, promotes the speedy transmission of information and might play a role in supporting the humpback's complex social life and sophisticated ability to communicate.
A study in the current edition of the Anatomical Record reports that the humpback brain contains "islands" of neural cells in the cerebral cortex that are generally not seen in the smaller-toothed whales and dolphins but are found in primates and other large-brained whales.
The function of these "spindle" neurons is not well understood, but they are thought to be involved in processing thoughts and information and are affected by Alzheimer's disease and other debilitating brain disorders.
The study's authors, from the department of neuroscience at Mount Sinai School of Medicine in New York, say that spindle neurons probably first appeared in the common ancestor of humans about 15 million years ago and that they are found in great apes and humans but not in lesser apes and other primates.
In whales and dolphins they evolved earlier, possibly as early as 30 million years ago.
"Humpback whales exhibit complex social patterns that include intricate communication skills, coalition-formation, cooperation, cultural transmission and tool usage," the authors write. "It is thus likely that some of these abilities are related to comparable (tissue) complexity in brain organization in cetaceans and in hominids."
And evolved in other animals before humans even walked the earth?
So - at least some of - the evolution of brain can be tied to communication.
Enjoy.

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 64 of 65 (366563)
11-28-2006 5:00 PM
Reply to: Message 62 by Dr Adequate
11-28-2006 10:03 AM


Re: OOPS -- NOT so "special" after all?
Humpback whales use tools?
and clams got legs.
lol. Perhaps they did the etching for the dolphins?
So "Long, and Thanks for All the Fish"

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RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 65 of 65 (366568)
11-28-2006 5:29 PM
Reply to: Message 63 by Clark
11-28-2006 11:54 AM


Re: OOPS -- NOT so "special" after all?
I think you got it:
Page not Found (404 Error)
quote:
Compared to other baleen whales, the humpback whales that inhabit the Pacific coast of North America are unique. This population is characterized by a variety of remarkable feeding behaviors that include the production of loud, trumpet-like feeding calls. which are apparently used to herd schooling fishes such as the Pacific herring. These whales also demonstrate a type of tool use by deploying large bubble nets around fish schools or krill swarms. The prey is then devoured in a spectacular communal lunge as the whales come rocketing up through the center of the bubble net. Up to two dozen whales may take part in these lunging events, which turn the surface into a boiling caldron of bubbles, baleen, and bait fishes.
Click on the image for Quicktime of a feeding episode. (600k)
They do seem to be refering to whales with a list of tool abilities
http://news.nationalgeographic.com/...607_dolphin_tools.html
quote:
When researchers first saw something strange on the snout of a dolphin in Shark Bay, Western Australia, they thought it was a massive tumor. Now they say it provides the first evidence of a tool-use culture in marine mammals.
The object turned out to be a marine sponge broken off from the seabed. Later other bottlenose dolphins in Shark Bay were observed holding sponges over their beaks, and appeared to use them as a fishing tool.
Researchers now report this odd hunting technique originated in a single female and is passed from mother to daughter.
"The sponges probably act as a protective glove so the dolphins don't get stung by stonefish," Krtzen added. (The stonefish is a bottom dweller with highly venomous spines.) The sponge also appears to disturb fish hiding on the seabed. The dolphins then snap the fish up.
Hal Whitehead, a cetacean expert at Dalhousie University in Nova Scotia, Canada, points to bottlenose dolphins in Laguna, Brazil. These marine mammals coordinate their fishing efforts with local people. The dolphins herd schools of fish toward the beach, then signal to fishers to throw their nets. Any fish that escape swim straight into the mouths of the waiting bottlenoses.
Using people to herd the remaining fish back to them?
Humpback whales have brain cells also found i | EurekAlert!
quote:
"In spite of the relative scarcity of information on many cetacean species, it is important to note in this context that sperm whales, killer whales, and certainly humpback whales, exhibit complex social patterns that included intricate communication skills, coalition-formation, cooperation, cultural transmission and tool usage," the authors state. "It is thus likely that some of these abilities are related to comparable histologic complexity in brain organization in cetaceans and in hominids."
http://whale.wheelock.edu/archives/whalenet96/0044.html
quote:
When I was working with the White Marline Porpoise Circus in Port Aransas, Texas, I watched a dolphin there, named Pete (a bottlenose from Florida) do a similar thing. There was a pelican that would steal his fish if we threw them in the wrong direction, so it seemed Pete was tired of this.
One day between shows, we noticed about 8 fish, about 2-6 inches under the surface, in a circular ring, fairly evenly spaced. As they would sink, Pete went around to each one, pushing each one in turn, to the surface. The pelican appeared interested and wary. After about 10 minutes of this, the pelican flew and dove for one of the fish -- Pete grabbed him, and took him to the bottom and drowned him.
First time I had thought of this as "tool use". This shows that the behavior occurs in tursiops as well.
Knowledge of consequences as well eh?

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